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diff --git a/.venv/lib/python3.12/site-packages/networkx/generators/small.py b/.venv/lib/python3.12/site-packages/networkx/generators/small.py new file mode 100644 index 00000000..acd2fbc7 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/generators/small.py @@ -0,0 +1,993 @@ +""" +Various small and named graphs, together with some compact generators. + +""" + +__all__ = [ + "LCF_graph", + "bull_graph", + "chvatal_graph", + "cubical_graph", + "desargues_graph", + "diamond_graph", + "dodecahedral_graph", + "frucht_graph", + "heawood_graph", + "hoffman_singleton_graph", + "house_graph", + "house_x_graph", + "icosahedral_graph", + "krackhardt_kite_graph", + "moebius_kantor_graph", + "octahedral_graph", + "pappus_graph", + "petersen_graph", + "sedgewick_maze_graph", + "tetrahedral_graph", + "truncated_cube_graph", + "truncated_tetrahedron_graph", + "tutte_graph", +] + +from functools import wraps + +import networkx as nx +from networkx.exception import NetworkXError +from networkx.generators.classic import ( + complete_graph, + cycle_graph, + empty_graph, + path_graph, +) + + +def _raise_on_directed(func): + """ + A decorator which inspects the `create_using` argument and raises a + NetworkX exception when `create_using` is a DiGraph (class or instance) for + graph generators that do not support directed outputs. + """ + + @wraps(func) + def wrapper(*args, **kwargs): + if kwargs.get("create_using") is not None: + G = nx.empty_graph(create_using=kwargs["create_using"]) + if G.is_directed(): + raise NetworkXError("Directed Graph not supported") + return func(*args, **kwargs) + + return wrapper + + +@nx._dispatchable(graphs=None, returns_graph=True) +def LCF_graph(n, shift_list, repeats, create_using=None): + """ + Return the cubic graph specified in LCF notation. + + LCF (Lederberg-Coxeter-Fruchte) notation[1]_ is a compressed + notation used in the generation of various cubic Hamiltonian + graphs of high symmetry. See, for example, `dodecahedral_graph`, + `desargues_graph`, `heawood_graph` and `pappus_graph`. + + Nodes are drawn from ``range(n)``. Each node ``n_i`` is connected with + node ``n_i + shift % n`` where ``shift`` is given by cycling through + the input `shift_list` `repeat` s times. + + Parameters + ---------- + n : int + The starting graph is the `n`-cycle with nodes ``0, ..., n-1``. + The null graph is returned if `n` < 1. + + shift_list : list + A list of integer shifts mod `n`, ``[s1, s2, .., sk]`` + + repeats : int + Integer specifying the number of times that shifts in `shift_list` + are successively applied to each current node in the n-cycle + to generate an edge between ``n_current`` and ``n_current + shift mod n``. + + Returns + ------- + G : Graph + A graph instance created from the specified LCF notation. + + Examples + -------- + The utility graph $K_{3,3}$ + + >>> G = nx.LCF_graph(6, [3, -3], 3) + >>> G.edges() + EdgeView([(0, 1), (0, 5), (0, 3), (1, 2), (1, 4), (2, 3), (2, 5), (3, 4), (4, 5)]) + + The Heawood graph: + + >>> G = nx.LCF_graph(14, [5, -5], 7) + >>> nx.is_isomorphic(G, nx.heawood_graph()) + True + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/LCF_notation + + """ + if n <= 0: + return empty_graph(0, create_using) + + # start with the n-cycle + G = cycle_graph(n, create_using) + if G.is_directed(): + raise NetworkXError("Directed Graph not supported") + G.name = "LCF_graph" + nodes = sorted(G) + + n_extra_edges = repeats * len(shift_list) + # edges are added n_extra_edges times + # (not all of these need be new) + if n_extra_edges < 1: + return G + + for i in range(n_extra_edges): + shift = shift_list[i % len(shift_list)] # cycle through shift_list + v1 = nodes[i % n] # cycle repeatedly through nodes + v2 = nodes[(i + shift) % n] + G.add_edge(v1, v2) + return G + + +# ------------------------------------------------------------------------------- +# Various small and named graphs +# ------------------------------------------------------------------------------- + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def bull_graph(create_using=None): + """ + Returns the Bull Graph + + The Bull Graph has 5 nodes and 5 edges. It is a planar undirected + graph in the form of a triangle with two disjoint pendant edges [1]_ + The name comes from the triangle and pendant edges representing + respectively the body and legs of a bull. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + A bull graph with 5 nodes + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Bull_graph. + + """ + G = nx.from_dict_of_lists( + {0: [1, 2], 1: [0, 2, 3], 2: [0, 1, 4], 3: [1], 4: [2]}, + create_using=create_using, + ) + G.name = "Bull Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def chvatal_graph(create_using=None): + """ + Returns the Chvátal Graph + + The Chvátal Graph is an undirected graph with 12 nodes and 24 edges [1]_. + It has 370 distinct (directed) Hamiltonian cycles, giving a unique generalized + LCF notation of order 4, two of order 6 , and 43 of order 1 [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + The Chvátal graph with 12 nodes and 24 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Chv%C3%A1tal_graph + .. [2] https://mathworld.wolfram.com/ChvatalGraph.html + + """ + G = nx.from_dict_of_lists( + { + 0: [1, 4, 6, 9], + 1: [2, 5, 7], + 2: [3, 6, 8], + 3: [4, 7, 9], + 4: [5, 8], + 5: [10, 11], + 6: [10, 11], + 7: [8, 11], + 8: [10], + 9: [10, 11], + }, + create_using=create_using, + ) + G.name = "Chvatal Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def cubical_graph(create_using=None): + """ + Returns the 3-regular Platonic Cubical Graph + + The skeleton of the cube (the nodes and edges) form a graph, with 8 + nodes, and 12 edges. It is a special case of the hypercube graph. + It is one of 5 Platonic graphs, each a skeleton of its + Platonic solid [1]_. + Such graphs arise in parallel processing in computers. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + A cubical graph with 8 nodes and 12 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Cube#Cubical_graph + + """ + G = nx.from_dict_of_lists( + { + 0: [1, 3, 4], + 1: [0, 2, 7], + 2: [1, 3, 6], + 3: [0, 2, 5], + 4: [0, 5, 7], + 5: [3, 4, 6], + 6: [2, 5, 7], + 7: [1, 4, 6], + }, + create_using=create_using, + ) + G.name = "Platonic Cubical Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def desargues_graph(create_using=None): + """ + Returns the Desargues Graph + + The Desargues Graph is a non-planar, distance-transitive cubic graph + with 20 nodes and 30 edges [1]_. + It is a symmetric graph. It can be represented in LCF notation + as [5,-5,9,-9]^5 [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Desargues Graph with 20 nodes and 30 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Desargues_graph + .. [2] https://mathworld.wolfram.com/DesarguesGraph.html + """ + G = LCF_graph(20, [5, -5, 9, -9], 5, create_using) + G.name = "Desargues Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def diamond_graph(create_using=None): + """ + Returns the Diamond graph + + The Diamond Graph is planar undirected graph with 4 nodes and 5 edges. + It is also sometimes known as the double triangle graph or kite graph [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Diamond Graph with 4 nodes and 5 edges + + References + ---------- + .. [1] https://mathworld.wolfram.com/DiamondGraph.html + """ + G = nx.from_dict_of_lists( + {0: [1, 2], 1: [0, 2, 3], 2: [0, 1, 3], 3: [1, 2]}, create_using=create_using + ) + G.name = "Diamond Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def dodecahedral_graph(create_using=None): + """ + Returns the Platonic Dodecahedral graph. + + The dodecahedral graph has 20 nodes and 30 edges. The skeleton of the + dodecahedron forms a graph. It is one of 5 Platonic graphs [1]_. + It can be described in LCF notation as: + ``[10, 7, 4, -4, -7, 10, -4, 7, -7, 4]^2`` [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Dodecahedral Graph with 20 nodes and 30 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Regular_dodecahedron#Dodecahedral_graph + .. [2] https://mathworld.wolfram.com/DodecahedralGraph.html + + """ + G = LCF_graph(20, [10, 7, 4, -4, -7, 10, -4, 7, -7, 4], 2, create_using) + G.name = "Dodecahedral Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def frucht_graph(create_using=None): + """ + Returns the Frucht Graph. + + The Frucht Graph is the smallest cubical graph whose + automorphism group consists only of the identity element [1]_. + It has 12 nodes and 18 edges and no nontrivial symmetries. + It is planar and Hamiltonian [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Frucht Graph with 12 nodes and 18 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Frucht_graph + .. [2] https://mathworld.wolfram.com/FruchtGraph.html + + """ + G = cycle_graph(7, create_using) + G.add_edges_from( + [ + [0, 7], + [1, 7], + [2, 8], + [3, 9], + [4, 9], + [5, 10], + [6, 10], + [7, 11], + [8, 11], + [8, 9], + [10, 11], + ] + ) + + G.name = "Frucht Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def heawood_graph(create_using=None): + """ + Returns the Heawood Graph, a (3,6) cage. + + The Heawood Graph is an undirected graph with 14 nodes and 21 edges, + named after Percy John Heawood [1]_. + It is cubic symmetric, nonplanar, Hamiltonian, and can be represented + in LCF notation as ``[5,-5]^7`` [2]_. + It is the unique (3,6)-cage: the regular cubic graph of girth 6 with + minimal number of vertices [3]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Heawood Graph with 14 nodes and 21 edges + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Heawood_graph + .. [2] https://mathworld.wolfram.com/HeawoodGraph.html + .. [3] https://www.win.tue.nl/~aeb/graphs/Heawood.html + + """ + G = LCF_graph(14, [5, -5], 7, create_using) + G.name = "Heawood Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def hoffman_singleton_graph(): + """ + Returns the Hoffman-Singleton Graph. + + The Hoffman–Singleton graph is a symmetrical undirected graph + with 50 nodes and 175 edges. + All indices lie in ``Z % 5``: that is, the integers mod 5 [1]_. + It is the only regular graph of vertex degree 7, diameter 2, and girth 5. + It is the unique (7,5)-cage graph and Moore graph, and contains many + copies of the Petersen graph [2]_. + + Returns + ------- + G : networkx Graph + Hoffman–Singleton Graph with 50 nodes and 175 edges + + Notes + ----- + Constructed from pentagon and pentagram as follows: Take five pentagons $P_h$ + and five pentagrams $Q_i$ . Join vertex $j$ of $P_h$ to vertex $h·i+j$ of $Q_i$ [3]_. + + References + ---------- + .. [1] https://blogs.ams.org/visualinsight/2016/02/01/hoffman-singleton-graph/ + .. [2] https://mathworld.wolfram.com/Hoffman-SingletonGraph.html + .. [3] https://en.wikipedia.org/wiki/Hoffman%E2%80%93Singleton_graph + + """ + G = nx.Graph() + for i in range(5): + for j in range(5): + G.add_edge(("pentagon", i, j), ("pentagon", i, (j - 1) % 5)) + G.add_edge(("pentagon", i, j), ("pentagon", i, (j + 1) % 5)) + G.add_edge(("pentagram", i, j), ("pentagram", i, (j - 2) % 5)) + G.add_edge(("pentagram", i, j), ("pentagram", i, (j + 2) % 5)) + for k in range(5): + G.add_edge(("pentagon", i, j), ("pentagram", k, (i * k + j) % 5)) + G = nx.convert_node_labels_to_integers(G) + G.name = "Hoffman-Singleton Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def house_graph(create_using=None): + """ + Returns the House graph (square with triangle on top) + + The house graph is a simple undirected graph with + 5 nodes and 6 edges [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + House graph in the form of a square with a triangle on top + + References + ---------- + .. [1] https://mathworld.wolfram.com/HouseGraph.html + """ + G = nx.from_dict_of_lists( + {0: [1, 2], 1: [0, 3], 2: [0, 3, 4], 3: [1, 2, 4], 4: [2, 3]}, + create_using=create_using, + ) + G.name = "House Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def house_x_graph(create_using=None): + """ + Returns the House graph with a cross inside the house square. + + The House X-graph is the House graph plus the two edges connecting diagonally + opposite vertices of the square base. It is also one of the two graphs + obtained by removing two edges from the pentatope graph [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + House graph with diagonal vertices connected + + References + ---------- + .. [1] https://mathworld.wolfram.com/HouseGraph.html + """ + G = house_graph(create_using) + G.add_edges_from([(0, 3), (1, 2)]) + G.name = "House-with-X-inside Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def icosahedral_graph(create_using=None): + """ + Returns the Platonic Icosahedral graph. + + The icosahedral graph has 12 nodes and 30 edges. It is a Platonic graph + whose nodes have the connectivity of the icosahedron. It is undirected, + regular and Hamiltonian [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Icosahedral graph with 12 nodes and 30 edges. + + References + ---------- + .. [1] https://mathworld.wolfram.com/IcosahedralGraph.html + """ + G = nx.from_dict_of_lists( + { + 0: [1, 5, 7, 8, 11], + 1: [2, 5, 6, 8], + 2: [3, 6, 8, 9], + 3: [4, 6, 9, 10], + 4: [5, 6, 10, 11], + 5: [6, 11], + 7: [8, 9, 10, 11], + 8: [9], + 9: [10], + 10: [11], + }, + create_using=create_using, + ) + G.name = "Platonic Icosahedral Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def krackhardt_kite_graph(create_using=None): + """ + Returns the Krackhardt Kite Social Network. + + A 10 actor social network introduced by David Krackhardt + to illustrate different centrality measures [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Krackhardt Kite graph with 10 nodes and 18 edges + + Notes + ----- + The traditional labeling is: + Andre=1, Beverley=2, Carol=3, Diane=4, + Ed=5, Fernando=6, Garth=7, Heather=8, Ike=9, Jane=10. + + References + ---------- + .. [1] Krackhardt, David. "Assessing the Political Landscape: Structure, + Cognition, and Power in Organizations". Administrative Science Quarterly. + 35 (2): 342–369. doi:10.2307/2393394. JSTOR 2393394. June 1990. + + """ + G = nx.from_dict_of_lists( + { + 0: [1, 2, 3, 5], + 1: [0, 3, 4, 6], + 2: [0, 3, 5], + 3: [0, 1, 2, 4, 5, 6], + 4: [1, 3, 6], + 5: [0, 2, 3, 6, 7], + 6: [1, 3, 4, 5, 7], + 7: [5, 6, 8], + 8: [7, 9], + 9: [8], + }, + create_using=create_using, + ) + G.name = "Krackhardt Kite Social Network" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def moebius_kantor_graph(create_using=None): + """ + Returns the Moebius-Kantor graph. + + The Möbius-Kantor graph is the cubic symmetric graph on 16 nodes. + Its LCF notation is [5,-5]^8, and it is isomorphic to the generalized + Petersen graph [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Moebius-Kantor graph + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/M%C3%B6bius%E2%80%93Kantor_graph + + """ + G = LCF_graph(16, [5, -5], 8, create_using) + G.name = "Moebius-Kantor Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def octahedral_graph(create_using=None): + """ + Returns the Platonic Octahedral graph. + + The octahedral graph is the 6-node 12-edge Platonic graph having the + connectivity of the octahedron [1]_. If 6 couples go to a party, + and each person shakes hands with every person except his or her partner, + then this graph describes the set of handshakes that take place; + for this reason it is also called the cocktail party graph [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Octahedral graph + + References + ---------- + .. [1] https://mathworld.wolfram.com/OctahedralGraph.html + .. [2] https://en.wikipedia.org/wiki/Tur%C3%A1n_graph#Special_cases + + """ + G = nx.from_dict_of_lists( + {0: [1, 2, 3, 4], 1: [2, 3, 5], 2: [4, 5], 3: [4, 5], 4: [5]}, + create_using=create_using, + ) + G.name = "Platonic Octahedral Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def pappus_graph(): + """ + Returns the Pappus graph. + + The Pappus graph is a cubic symmetric distance-regular graph with 18 nodes + and 27 edges. It is Hamiltonian and can be represented in LCF notation as + [5,7,-7,7,-7,-5]^3 [1]_. + + Returns + ------- + G : networkx Graph + Pappus graph + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Pappus_graph + """ + G = LCF_graph(18, [5, 7, -7, 7, -7, -5], 3) + G.name = "Pappus Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def petersen_graph(create_using=None): + """ + Returns the Petersen graph. + + The Peterson graph is a cubic, undirected graph with 10 nodes and 15 edges [1]_. + Julius Petersen constructed the graph as the smallest counterexample + against the claim that a connected bridgeless cubic graph + has an edge colouring with three colours [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Petersen graph + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Petersen_graph + .. [2] https://www.win.tue.nl/~aeb/drg/graphs/Petersen.html + """ + G = nx.from_dict_of_lists( + { + 0: [1, 4, 5], + 1: [0, 2, 6], + 2: [1, 3, 7], + 3: [2, 4, 8], + 4: [3, 0, 9], + 5: [0, 7, 8], + 6: [1, 8, 9], + 7: [2, 5, 9], + 8: [3, 5, 6], + 9: [4, 6, 7], + }, + create_using=create_using, + ) + G.name = "Petersen Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def sedgewick_maze_graph(create_using=None): + """ + Return a small maze with a cycle. + + This is the maze used in Sedgewick, 3rd Edition, Part 5, Graph + Algorithms, Chapter 18, e.g. Figure 18.2 and following [1]_. + Nodes are numbered 0,..,7 + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Small maze with a cycle + + References + ---------- + .. [1] Figure 18.2, Chapter 18, Graph Algorithms (3rd Ed), Sedgewick + """ + G = empty_graph(0, create_using) + G.add_nodes_from(range(8)) + G.add_edges_from([[0, 2], [0, 7], [0, 5]]) + G.add_edges_from([[1, 7], [2, 6]]) + G.add_edges_from([[3, 4], [3, 5]]) + G.add_edges_from([[4, 5], [4, 7], [4, 6]]) + G.name = "Sedgewick Maze" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def tetrahedral_graph(create_using=None): + """ + Returns the 3-regular Platonic Tetrahedral graph. + + Tetrahedral graph has 4 nodes and 6 edges. It is a + special case of the complete graph, K4, and wheel graph, W4. + It is one of the 5 platonic graphs [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Tetrahedral Graph + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Tetrahedron#Tetrahedral_graph + + """ + G = complete_graph(4, create_using) + G.name = "Platonic Tetrahedral Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def truncated_cube_graph(create_using=None): + """ + Returns the skeleton of the truncated cube. + + The truncated cube is an Archimedean solid with 14 regular + faces (6 octagonal and 8 triangular), 36 edges and 24 nodes [1]_. + The truncated cube is created by truncating (cutting off) the tips + of the cube one third of the way into each edge [2]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Skeleton of the truncated cube + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Truncated_cube + .. [2] https://www.coolmath.com/reference/polyhedra-truncated-cube + + """ + G = nx.from_dict_of_lists( + { + 0: [1, 2, 4], + 1: [11, 14], + 2: [3, 4], + 3: [6, 8], + 4: [5], + 5: [16, 18], + 6: [7, 8], + 7: [10, 12], + 8: [9], + 9: [17, 20], + 10: [11, 12], + 11: [14], + 12: [13], + 13: [21, 22], + 14: [15], + 15: [19, 23], + 16: [17, 18], + 17: [20], + 18: [19], + 19: [23], + 20: [21], + 21: [22], + 22: [23], + }, + create_using=create_using, + ) + G.name = "Truncated Cube Graph" + return G + + +@nx._dispatchable(graphs=None, returns_graph=True) +def truncated_tetrahedron_graph(create_using=None): + """ + Returns the skeleton of the truncated Platonic tetrahedron. + + The truncated tetrahedron is an Archimedean solid with 4 regular hexagonal faces, + 4 equilateral triangle faces, 12 nodes and 18 edges. It can be constructed by truncating + all 4 vertices of a regular tetrahedron at one third of the original edge length [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Skeleton of the truncated tetrahedron + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Truncated_tetrahedron + + """ + G = path_graph(12, create_using) + G.add_edges_from([(0, 2), (0, 9), (1, 6), (3, 11), (4, 11), (5, 7), (8, 10)]) + G.name = "Truncated Tetrahedron Graph" + return G + + +@_raise_on_directed +@nx._dispatchable(graphs=None, returns_graph=True) +def tutte_graph(create_using=None): + """ + Returns the Tutte graph. + + The Tutte graph is a cubic polyhedral, non-Hamiltonian graph. It has + 46 nodes and 69 edges. + It is a counterexample to Tait's conjecture that every 3-regular polyhedron + has a Hamiltonian cycle. + It can be realized geometrically from a tetrahedron by multiply truncating + three of its vertices [1]_. + + Parameters + ---------- + create_using : NetworkX graph constructor, optional (default=nx.Graph) + Graph type to create. If graph instance, then cleared before populated. + + Returns + ------- + G : networkx Graph + Tutte graph + + References + ---------- + .. [1] https://en.wikipedia.org/wiki/Tutte_graph + """ + G = nx.from_dict_of_lists( + { + 0: [1, 2, 3], + 1: [4, 26], + 2: [10, 11], + 3: [18, 19], + 4: [5, 33], + 5: [6, 29], + 6: [7, 27], + 7: [8, 14], + 8: [9, 38], + 9: [10, 37], + 10: [39], + 11: [12, 39], + 12: [13, 35], + 13: [14, 15], + 14: [34], + 15: [16, 22], + 16: [17, 44], + 17: [18, 43], + 18: [45], + 19: [20, 45], + 20: [21, 41], + 21: [22, 23], + 22: [40], + 23: [24, 27], + 24: [25, 32], + 25: [26, 31], + 26: [33], + 27: [28], + 28: [29, 32], + 29: [30], + 30: [31, 33], + 31: [32], + 34: [35, 38], + 35: [36], + 36: [37, 39], + 37: [38], + 40: [41, 44], + 41: [42], + 42: [43, 45], + 43: [44], + }, + create_using=create_using, + ) + G.name = "Tutte's Graph" + return G |